angular-cn/packages/core/test/test_bed_spec.ts

/**
 * @license
 * Copyright Google Inc. All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */

import {APP_INITIALIZER, ChangeDetectorRef, Compiler, Component, Directive, ErrorHandler, Inject, Injectable, InjectionToken, Injector, Input, LOCALE_ID, ModuleWithProviders, NgModule, Optional, Pipe, Type, ViewChild, ɵsetClassMetadata as setClassMetadata, ɵɵdefineComponent as defineComponent, ɵɵdefineInjector as defineInjector, ɵɵdefineNgModule as defineNgModule, ɵɵsetNgModuleScope as setNgModuleScope, ɵɵtext as text} from '@angular/core';
import {TestBed, getTestBed} from '@angular/core/testing/src/test_bed';
import {By} from '@angular/platform-browser';
import {expect} from '@angular/platform-browser/testing/src/matchers';
import {onlyInIvy} from '@angular/private/testing';

const NAME = new InjectionToken<string>('name');

@Injectable({providedIn: 'root'})
class SimpleService {
  static ngOnDestroyCalls: number = 0;
  id: number = 1;
  ngOnDestroy() { SimpleService.ngOnDestroyCalls++; }
}

// -- module: HWModule
@Component({
  selector: 'hello-world',
  template: '<greeting-cmp></greeting-cmp>',
})
export class HelloWorld {
}

// -- module: Greeting
@Component({
  selector: 'greeting-cmp',
  template: 'Hello {{ name }}',
})
export class GreetingCmp {
  name: string;

  constructor(
      @Inject(NAME) @Optional() name: string,
      @Inject(SimpleService) @Optional() service: SimpleService) {
    this.name = name || 'nobody!';
  }
}

@Component({
  selector: 'cmp-with-providers',
  template: '<hello-world></hello-world>',
  providers: [
    SimpleService,  //
    {provide: NAME, useValue: `from Component`}
  ]
})
class CmpWithProviders {
}

@NgModule({
  declarations: [GreetingCmp],
  exports: [GreetingCmp],
})
export class GreetingModule {
}

@Component({selector: 'simple-cmp', template: '<b>simple</b>'})
export class SimpleCmp {
}

@Component({selector: 'with-refs-cmp', template: '<div #firstDiv></div>'})
export class WithRefsCmp {
}

@Component({selector: 'inherited-cmp', template: 'inherited'})
export class InheritedCmp extends SimpleCmp {
}

@Directive({selector: '[hostBindingDir]', host: {'[id]': 'id'}})
export class HostBindingDir {
  id = 'one';
}

@Component({
  selector: 'component-with-prop-bindings',
  template: `
    <div hostBindingDir [title]="title" [attr.aria-label]="label"></div>
    <p title="( {{ label }} - {{ title }} )" [attr.aria-label]="label" id="[ {{ label }} ] [ {{ title }} ]">
    </p>
  `
})
export class ComponentWithPropBindings {
  title = 'some title';
  label = 'some label';
}

@Component({
  selector: 'simple-app',
  template: `
    <simple-cmp></simple-cmp> - <inherited-cmp></inherited-cmp>
  `
})
export class SimpleApp {
}

@Component({selector: 'inline-template', template: '<p>Hello</p>'})
export class ComponentWithInlineTemplate {
}

@NgModule({
  declarations: [
    HelloWorld, SimpleCmp, WithRefsCmp, InheritedCmp, SimpleApp, ComponentWithPropBindings,
    HostBindingDir, CmpWithProviders
  ],
  imports: [GreetingModule],
  providers: [
    {provide: NAME, useValue: 'World!'},
  ]
})
export class HelloWorldModule {
}

describe('TestBed', () => {
  beforeEach(() => {
    getTestBed().resetTestingModule();
    TestBed.configureTestingModule({imports: [HelloWorldModule]});
  });

  it('should compile and render a component', () => {
    const hello = TestBed.createComponent(HelloWorld);
    hello.detectChanges();

    expect(hello.nativeElement).toHaveText('Hello World!');
  });

  it('should give access to the component instance', () => {
    const hello = TestBed.createComponent(HelloWorld);
    hello.detectChanges();

    expect(hello.componentInstance).toBeAnInstanceOf(HelloWorld);
  });

  it('should give the ability to query by css', () => {
    const hello = TestBed.createComponent(HelloWorld);
    hello.detectChanges();

    const greetingByCss = hello.debugElement.query(By.css('greeting-cmp'));
    expect(greetingByCss.nativeElement).toHaveText('Hello World!');
    expect(greetingByCss.componentInstance).toBeAnInstanceOf(GreetingCmp);
  });

  it('should give the ability to trigger the change detection', () => {
    const hello = TestBed.createComponent(HelloWorld);

    hello.detectChanges();
    const greetingByCss = hello.debugElement.query(By.css('greeting-cmp'));
    expect(greetingByCss.nativeElement).toHaveText('Hello World!');

    greetingByCss.componentInstance.name = 'TestBed!';
    hello.detectChanges();
    expect(greetingByCss.nativeElement).toHaveText('Hello TestBed!');
  });

  it('should give the ability to access property bindings on a node', () => {
    const fixture = TestBed.createComponent(ComponentWithPropBindings);
    fixture.detectChanges();

    const divElement = fixture.debugElement.query(By.css('div'));
    expect(divElement.properties.id).toEqual('one');
    expect(divElement.properties.title).toEqual('some title');
  });

  it('should give the ability to access interpolated properties on a node', () => {
    const fixture = TestBed.createComponent(ComponentWithPropBindings);
    fixture.detectChanges();

    const paragraphEl = fixture.debugElement.query(By.css('p'));
    expect(paragraphEl.properties.title).toEqual('( some label - some title )');
    expect(paragraphEl.properties.id).toEqual('[ some label ] [ some title ]');
  });

  it('should give access to the node injector', () => {
    const fixture = TestBed.createComponent(HelloWorld);
    fixture.detectChanges();
    const injector = fixture.debugElement.query(By.css('greeting-cmp')).injector;

    // from the node injector
    const greetingCmp = injector.get(GreetingCmp);
    expect(greetingCmp.constructor).toBe(GreetingCmp);

    // from the node injector (inherited from a parent node)
    const helloWorldCmp = injector.get(HelloWorld);
    expect(fixture.componentInstance).toBe(helloWorldCmp);

    const nameInjected = injector.get(NAME);
    expect(nameInjected).toEqual('World!');
  });

  it('should give access to the node injector for root node', () => {
    const hello = TestBed.createComponent(HelloWorld);
    hello.detectChanges();
    const injector = hello.debugElement.injector;

    // from the node injector
    const helloInjected = injector.get(HelloWorld);
    expect(helloInjected).toBe(hello.componentInstance);

    // from the module injector
    const nameInjected = injector.get(NAME);
    expect(nameInjected).toEqual('World!');
  });

  it('should give access to local refs on a node', () => {
    const withRefsCmp = TestBed.createComponent(WithRefsCmp);
    const firstDivDebugEl = withRefsCmp.debugElement.query(By.css('div'));
    // assert that a native element is referenced by a local ref
    expect(firstDivDebugEl.references.firstDiv.tagName.toLowerCase()).toBe('div');
  });

  it('should give the ability to query by directive', () => {
    const hello = TestBed.createComponent(HelloWorld);
    hello.detectChanges();

    const greetingByDirective = hello.debugElement.query(By.directive(GreetingCmp));
    expect(greetingByDirective.componentInstance).toBeAnInstanceOf(GreetingCmp);
  });

  it('allow to override a template', () => {
    // use original template when there is no override
    let hello = TestBed.createComponent(HelloWorld);
    hello.detectChanges();
    expect(hello.nativeElement).toHaveText('Hello World!');

    // override the template
    getTestBed().resetTestingModule();
    TestBed.configureTestingModule({imports: [HelloWorldModule]});
    TestBed.overrideComponent(GreetingCmp, {set: {template: `Bonjour {{ name }}`}});
    hello = TestBed.createComponent(HelloWorld);
    hello.detectChanges();
    expect(hello.nativeElement).toHaveText('Bonjour World!');

    // restore the original template by calling `.resetTestingModule()`
    getTestBed().resetTestingModule();
    TestBed.configureTestingModule({imports: [HelloWorldModule]});
    hello = TestBed.createComponent(HelloWorld);
    hello.detectChanges();
    expect(hello.nativeElement).toHaveText('Hello World!');
  });

  it('should run `APP_INITIALIZER` before accessing `LOCALE_ID` provider', () => {
    let locale: string = '';
    @NgModule({
      providers: [
        {provide: APP_INITIALIZER, useValue: () => locale = 'fr-FR', multi: true},
        {provide: LOCALE_ID, useFactory: () => locale}
      ]
    })
    class TestModule {
    }

    TestBed.configureTestingModule({imports: [TestModule]});
    expect(TestBed.inject(LOCALE_ID)).toBe('fr-FR');
  });

  it('allow to override a provider', () => {
    TestBed.overrideProvider(NAME, {useValue: 'injected World!'});
    const hello = TestBed.createComponent(HelloWorld);
    hello.detectChanges();
    expect(hello.nativeElement).toHaveText('Hello injected World!');
  });

  it('uses the most recent provider override', () => {
    TestBed.overrideProvider(NAME, {useValue: 'injected World!'});
    TestBed.overrideProvider(NAME, {useValue: 'injected World a second time!'});
    const hello = TestBed.createComponent(HelloWorld);
    hello.detectChanges();
    expect(hello.nativeElement).toHaveText('Hello injected World a second time!');
  });

  it('overrides a providers in an array', () => {
    TestBed.configureTestingModule({
      imports: [HelloWorldModule],
      providers: [
        [{provide: NAME, useValue: 'injected World!'}],
      ]
    });
    TestBed.overrideProvider(NAME, {useValue: 'injected World a second time!'});
    const hello = TestBed.createComponent(HelloWorld);
    hello.detectChanges();
    expect(hello.nativeElement).toHaveText('Hello injected World a second time!');
  });

  it('should not call ngOnDestroy for a service that was overridden', () => {
    SimpleService.ngOnDestroyCalls = 0;

    TestBed.overrideProvider(SimpleService, {useValue: {id: 2, ngOnDestroy: () => {}}});
    const fixture = TestBed.createComponent(CmpWithProviders);
    fixture.detectChanges();

    const service = TestBed.inject(SimpleService);
    expect(service.id).toBe(2);

    fixture.destroy();

    // verify that original `ngOnDestroy` was not called
    expect(SimpleService.ngOnDestroyCalls).toBe(0);
  });

  describe('module overrides using TestBed.overrideModule', () => {
    @Component({
      selector: 'test-cmp',
      template: '...',
    })
    class TestComponent {
      testField = 'default';
    }

    @NgModule({
      declarations: [TestComponent],
      exports: [TestComponent],
    })
    class TestModule {
    }

    @Component({
      selector: 'app-root',
      template: `<test-cmp #testCmpCtrl></test-cmp>`,
    })
    class AppComponent {
      @ViewChild('testCmpCtrl', {static: true}) testCmpCtrl !: TestComponent;
    }

    @NgModule({
      declarations: [AppComponent],
      imports: [TestModule],
    })
    class AppModule {
    }
    @Component({
      selector: 'test-cmp',
      template: '...',
    })
    class MockTestComponent {
      testField = 'overwritten';
    }

    it('should allow declarations override', () => {
      TestBed.configureTestingModule({
        imports: [AppModule],
      });
      // replace TestComponent with MockTestComponent
      TestBed.overrideModule(TestModule, {
        remove: {declarations: [TestComponent], exports: [TestComponent]},
        add: {declarations: [MockTestComponent], exports: [MockTestComponent]}
      });
      const fixture = TestBed.createComponent(AppComponent);
      const app = fixture.componentInstance;
      expect(app.testCmpCtrl.testField).toBe('overwritten');
    });
  });

  describe('multi providers', () => {
    const multiToken = new InjectionToken<string[]>('multiToken');
    const singleToken = new InjectionToken<string>('singleToken');
    const multiTokenToOverrideAtModuleLevel =
        new InjectionToken<string[]>('moduleLevelMultiOverride');
    @NgModule({providers: [{provide: multiToken, useValue: 'valueFromModule', multi: true}]})
    class MyModule {
    }

    @NgModule({
      providers: [
        {provide: singleToken, useValue: 't1'}, {
          provide: multiTokenToOverrideAtModuleLevel,
          useValue: 'multiTokenToOverrideAtModuleLevelOriginal',
          multi: true
        },
        {provide: multiToken, useValue: 'valueFromModule2', multi: true},
        {provide: multiToken, useValue: 'secondValueFromModule2', multi: true}
      ]
    })
    class MyModule2 {
    }

    beforeEach(() => {
      TestBed.configureTestingModule({
        imports: [
          MyModule, {
            ngModule: MyModule2,
            providers:
                [{provide: multiTokenToOverrideAtModuleLevel, useValue: 'override', multi: true}]
          }
        ],
      });
    });

    it('is preserved when other provider is overridden', () => {
      TestBed.overrideProvider(singleToken, {useValue: ''});
      expect(TestBed.inject(multiToken).length).toEqual(3);
      expect(TestBed.inject(multiTokenToOverrideAtModuleLevel).length).toEqual(2);
      expect(TestBed.inject(multiTokenToOverrideAtModuleLevel)).toEqual([
        'multiTokenToOverrideAtModuleLevelOriginal', 'override'
      ]);
    });

    it('overridden with an array', () => {
      const overrideValue = ['override'];
      TestBed.overrideProvider(multiToken, { useValue: overrideValue, multi: true } as any);

      const value = TestBed.inject(multiToken);
      expect(value.length).toEqual(overrideValue.length);
      expect(value).toEqual(overrideValue);
    });

    it('overridden with a non-array', () => {
      // This is actually invalid because multi providers return arrays. We have this here so we can
      // ensure Ivy behaves the same as VE does currently.
      const overrideValue = 'override';
      TestBed.overrideProvider(multiToken, { useValue: overrideValue, multi: true } as any);

      const value = TestBed.inject(multiToken);
      expect(value.length).toEqual(overrideValue.length);
      expect(value).toEqual(overrideValue as {} as string[]);
    });
  });

  describe('overrides providers in ModuleWithProviders', () => {
    const TOKEN = new InjectionToken<string[]>('token');
    @NgModule()
    class MyMod {
      static multi = false;

      static forRoot() {
        return {
          ngModule: MyMod,
          providers: [{provide: TOKEN, multi: MyMod.multi, useValue: 'forRootValue'}]
        };
      }
    }

    beforeEach(() => MyMod.multi = true);

    it('when provider is a "regular" provider', () => {
      MyMod.multi = false;
      @NgModule({imports: [MyMod.forRoot()]})
      class MyMod2 {
      }
      TestBed.configureTestingModule({imports: [MyMod2]});
      TestBed.overrideProvider(TOKEN, {useValue: ['override']});
      expect(TestBed.inject(TOKEN)).toEqual(['override']);
    });

    it('when provider is multi', () => {
      @NgModule({imports: [MyMod.forRoot()]})
      class MyMod2 {
      }
      TestBed.configureTestingModule({imports: [MyMod2]});
      TestBed.overrideProvider(TOKEN, {useValue: ['override']});
      expect(TestBed.inject(TOKEN)).toEqual(['override']);
    });

    it('restores the original value', () => {
      @NgModule({imports: [MyMod.forRoot()]})
      class MyMod2 {
      }
      TestBed.configureTestingModule({imports: [MyMod2]});
      TestBed.overrideProvider(TOKEN, {useValue: ['override']});
      expect(TestBed.inject(TOKEN)).toEqual(['override']);

      TestBed.resetTestingModule();
      TestBed.configureTestingModule({imports: [MyMod2]});
      expect(TestBed.inject(TOKEN)).toEqual(['forRootValue']);
    });
  });

  it('should allow overriding a provider defined via ModuleWithProviders (using TestBed.overrideProvider)',
     () => {
       const serviceOverride = {
         get() { return 'override'; },
       };

       @Injectable({providedIn: 'root'})
       class MyService {
         get() { return 'original'; }
       }

       @NgModule({})
       class MyModule {
         static forRoot(): ModuleWithProviders<MyModule> {
           return {
             ngModule: MyModule,
             providers: [MyService],
           };
         }
       }
       TestBed.overrideProvider(MyService, {useValue: serviceOverride});
       TestBed.configureTestingModule({
         imports: [MyModule.forRoot()],
       });

       const service = TestBed.inject(MyService);
       expect(service.get()).toEqual('override');
     });

  it('should handle overrides for a provider that has `ChangeDetectorRef` as a dependency', () => {
    // Note: we specifically check an @Injectable with `ChangeDetectorRef` here due to the fact that
    // in Ivy there is a special instruction that injects `ChangeDetectorRef` token for Pipes
    // (ɵɵinjectPipeChangeDetectorRef) and using that function for other types causes problems,
    // for example when we try to override an @Injectable. The test below captures a use-case that
    // triggers a problem in case incompatible function is used to inject `ChangeDetectorRef` as a
    // dependency.
    @Injectable({providedIn: 'root'})
    class MyService {
      token = 'original';
      constructor(public cdr: ChangeDetectorRef) {}
    }

    TestBed.configureTestingModule({});
    TestBed.overrideProvider(MyService, {useValue: {token: 'override'}});

    const service = TestBed.inject(MyService);
    expect(service.token).toBe('override');
  });

  it('should allow overriding a provider defined via ModuleWithProviders (using TestBed.configureTestingModule)',
     () => {
       const serviceOverride = {
         get() { return 'override'; },
       };

       @Injectable({providedIn: 'root'})
       class MyService {
         get() { return 'original'; }
       }

       @NgModule({})
       class MyModule {
         static forRoot(): ModuleWithProviders<MyModule> {
           return {
             ngModule: MyModule,
             providers: [MyService],
           };
         }
       }
       TestBed.configureTestingModule({
         imports: [MyModule.forRoot()],
         providers: [{provide: MyService, useValue: serviceOverride}],
       });

       const service = TestBed.inject(MyService);
       expect(service.get()).toEqual('override');
     });

  it('overrides injectable that is using providedIn: AModule', () => {
    @NgModule()
    class ServiceModule {
    }
    @Injectable({providedIn: ServiceModule})
    class Service {
    }

    const fake = 'fake';
    TestBed.overrideProvider(Service, {useValue: fake});
    // Create an injector whose source is the ServiceModule, not DynamicTestModule.
    const ngModuleFactory = TestBed.inject(Compiler).compileModuleSync(ServiceModule);
    const injector = ngModuleFactory.create(TestBed.inject(Injector)).injector;

    const service = injector.get(Service);
    expect(service).toBe(fake);
  });

  it('allow to override multi provider', () => {
    const MY_TOKEN = new InjectionToken('MyProvider');
    class MyProvider {}

    @Component({selector: 'my-comp', template: ``})
    class MyComp {
      constructor(@Inject(MY_TOKEN) public myProviders: MyProvider[]) {}
    }

    TestBed.configureTestingModule({
      declarations: [MyComp],
      providers: [{provide: MY_TOKEN, useValue: {value: 'old provider'}, multi: true}]
    });

    const multiOverride = {useValue: [{value: 'new provider'}], multi: true};
    TestBed.overrideProvider(MY_TOKEN, multiOverride as any);

    const fixture = TestBed.createComponent(MyComp);
    expect(fixture.componentInstance.myProviders).toEqual([{value: 'new provider'}]);
  });

  it('should resolve components that are extended by other components', () => {
    // SimpleApp uses SimpleCmp in its template, which is extended by InheritedCmp
    const simpleApp = TestBed.createComponent(SimpleApp);
    simpleApp.detectChanges();
    expect(simpleApp.nativeElement).toHaveText('simple - inherited');
  });

  it('should not trigger change detection for ComponentA while calling TestBed.createComponent for ComponentB',
     () => {
       const log: string[] = [];
       @Component({
         selector: 'comp-a',
         template: '...',
       })
       class CompA {
         @Input() inputA: string = '';
         ngOnInit() { log.push('CompA:ngOnInit', this.inputA); }
       }

       @Component({
         selector: 'comp-b',
         template: '...',
       })
       class CompB {
         @Input() inputB: string = '';
         ngOnInit() { log.push('CompB:ngOnInit', this.inputB); }
       }

       TestBed.configureTestingModule({declarations: [CompA, CompB]});

       log.length = 0;
       const appA = TestBed.createComponent(CompA);
       appA.componentInstance.inputA = 'a';
       appA.autoDetectChanges();
       expect(log).toEqual(['CompA:ngOnInit', 'a']);

       log.length = 0;
       const appB = TestBed.createComponent(CompB);
       appB.componentInstance.inputB = 'b';
       appB.autoDetectChanges();
       expect(log).toEqual(['CompB:ngOnInit', 'b']);
     });

  it('should resolve components without async resources synchronously', (done) => {
    TestBed
        .configureTestingModule({
          declarations: [ComponentWithInlineTemplate],
        })
        .compileComponents()
        .then(done)
        .catch(error => {
          // This should not throw any errors. If an error is thrown, the test will fail.
          // Specifically use `catch` here to mark the test as done and *then* throw the error
          // so that the test isn't treated as a timeout.
          done();
          throw error;
        });

    // Intentionally call `createComponent` before `compileComponents` is resolved. We want this to
    // work for components that don't have any async resources (templateUrl, styleUrls).
    TestBed.createComponent(ComponentWithInlineTemplate);
  });

  it('should be able to override the ErrorHandler via an import', () => {
    class CustomErrorHandler {}

    @NgModule({providers: [{provide: ErrorHandler, useClass: CustomErrorHandler}]})
    class ProvidesErrorHandler {
    }

    getTestBed().resetTestingModule();
    TestBed.configureTestingModule({imports: [ProvidesErrorHandler, HelloWorldModule]});

    expect(TestBed.inject(ErrorHandler)).toEqual(jasmine.any(CustomErrorHandler));

  });

  it('should throw errors in CD', () => {
    @Component({selector: 'my-comp', template: ''})
    class MyComp {
      name !: {hello: string};

      ngOnInit() {
        // this should throw because this.name is undefined
        this.name.hello = 'hello';
      }
    }

    TestBed.configureTestingModule({declarations: [MyComp]});

    expect(() => {
      const fixture = TestBed.createComponent(MyComp);
      fixture.detectChanges();
    }).toThrowError();
  });

  // TODO(FW-1245): properly fix issue where errors in listeners aren't thrown and don't cause
  // tests to fail. This is an issue in both View Engine and Ivy, and may require a breaking
  // change to completely fix (since simple re-throwing breaks handlers in ngrx, etc).
  xit('should throw errors in listeners', () => {

    @Component({selector: 'my-comp', template: '<button (click)="onClick()">Click me</button>'})
    class MyComp {
      name !: {hello: string};

      onClick() {
        // this should throw because this.name is undefined
        this.name.hello = 'hello';
      }
    }

    TestBed.configureTestingModule({declarations: [MyComp]});
    const fixture = TestBed.createComponent(MyComp);
    fixture.detectChanges();

    expect(() => {
      const button = fixture.nativeElement.querySelector('button');
      button.click();
    }).toThrowError();
  });

  onlyInIvy('TestBed new feature to allow declaration and import of component')
      .it('should allow both the declaration and import of a component into the testing module',
          () => {
            // This test validates that a component (Outer) which is both declared and imported
            // (via its module) in the testing module behaves correctly. That is:
            //
            // 1) the component should be compiled in the scope of its original module.
            //
            // This condition is tested by having the component (Outer) use another component
            // (Inner) within its template. Thus, if it's compiled in the correct scope then the
            // text 'Inner' from the template of (Inner) should appear in the result.
            //
            // 2) the component should be available in the TestingModule scope.
            //
            // This condition is tested by attempting to use the component (Outer) inside a test
            // fixture component (Fixture) which is declared in the testing module only.

            @Component({
              selector: 'inner',
              template: 'Inner',
            })
            class Inner {
            }

            @Component({
              selector: 'outer',
              template: '<inner></inner>',
            })
            class Outer {
            }

            @NgModule({
              declarations: [Inner, Outer],
            })
            class Module {
            }

            @Component({
              template: '<outer></outer>',
              selector: 'fixture',
            })
            class Fixture {
            }

            TestBed.configureTestingModule({
              declarations: [Outer, Fixture],
              imports: [Module],
            });

            const fixture = TestBed.createComponent(Fixture);
            // The Outer component should have its template stamped out, and that template should
            // include a correct instance of the Inner component with the 'Inner' text from its
            // template.
            expect(fixture.nativeElement.innerHTML).toEqual('<outer><inner>Inner</inner></outer>');
          });

  onlyInIvy('Ivy-specific errors').describe('checking types before compiling them', () => {
    @Directive({
      selector: 'my-dir',
    })
    class MyDir {
    }

    @NgModule()
    class MyModule {
    }

    // [decorator, type, overrideFn]
    const cases: [string, Type<any>, string][] = [
      ['Component', MyDir, 'overrideComponent'],
      ['NgModule', MyDir, 'overrideModule'],
      ['Pipe', MyModule, 'overridePipe'],
      ['Directive', MyModule, 'overrideDirective'],
    ];
    cases.forEach(([decorator, type, overrideFn]) => {
      it(`should throw an error in case invalid type is used in ${overrideFn} function`, () => {
        TestBed.configureTestingModule({declarations: [MyDir]});
        expect(() => {
          (TestBed as any)[overrideFn](type, {});
          TestBed.createComponent(type);
        }).toThrowError(new RegExp(`class doesn't have @${decorator} decorator`, 'g'));
      });
    });
  });


  onlyInIvy('TestBed should handle AOT pre-compiled Components')
      .describe('AOT pre-compiled components', () => {
        /**
         * Function returns a class that represents AOT-compiled version of the following Component:
         *
         * @Component({
         *  selector: 'comp',
         *  templateUrl: './template.ng.html',
         *  styleUrls: ['./style.css']
         * })
         * class ComponentClass {}
         *
         * This is needed to closer match the behavior of AOT pre-compiled components (compiled
         * outside of TestBed) without changing TestBed state and/or Component metadata to compile
         * them via TestBed with external resources.
         */
        const getAOTCompiledComponent = () => {
          class ComponentClass {
            static ɵfac = () => new ComponentClass();
            static ɵcmp = defineComponent({
              type: ComponentClass,
              selectors: [['comp']],
              decls: 1,
              vars: 0,
              template: (rf: any, ctx: any) => {
                if (rf & 1) {
                  text(0, 'Some template');
                }
              },
              styles: ['body { margin: 0; }']
            });
          }
          setClassMetadata(
              ComponentClass, [{
                type: Component,
                args: [{
                  selector: 'comp',
                  templateUrl: './template.ng.html',
                  styleUrls: ['./style.css'],
                }]
              }],
              null, null);
          return ComponentClass;
        };

        it('should have an ability to override template', () => {
          const SomeComponent = getAOTCompiledComponent();
          TestBed.configureTestingModule({declarations: [SomeComponent]});
          TestBed.overrideTemplateUsingTestingModule(SomeComponent, 'Template override');
          const fixture = TestBed.createComponent(SomeComponent);
          expect(fixture.nativeElement.innerHTML).toBe('Template override');
        });

        it('should have an ability to override template with empty string', () => {
          const SomeComponent = getAOTCompiledComponent();
          TestBed.configureTestingModule({declarations: [SomeComponent]});
          TestBed.overrideTemplateUsingTestingModule(SomeComponent, '');
          const fixture = TestBed.createComponent(SomeComponent);
          expect(fixture.nativeElement.innerHTML).toBe('');
        });

        it('should allow component in both in declarations and imports', () => {
          const SomeComponent = getAOTCompiledComponent();

          // This is an AOT compiled module which declares (but does not export) SomeComponent.
          class ModuleClass {
            static ɵmod = defineNgModule({
              type: ModuleClass,
              declarations: [SomeComponent],
            });
          }

          @Component({
            template: '<comp></comp>',

            selector: 'fixture',
          })
          class TestFixture {
          }

          TestBed.configureTestingModule({
            // Here, SomeComponent is both declared, and then the module which declares it is
            // also imported. This used to be a duplicate declaration error, but is now interpreted
            // to mean:
            // 1) Compile (or reuse) SomeComponent in the context of its original NgModule
            // 2) Make SomeComponent available in the scope of the testing module, even if it wasn't
            //    originally exported from its NgModule.
            //
            // This allows TestFixture to use SomeComponent, which is asserted below.
            declarations: [SomeComponent, TestFixture],
            imports: [ModuleClass],
          });
          const fixture = TestBed.createComponent(TestFixture);
          // The regex avoids any issues with styling attributes.
          expect(fixture.nativeElement.innerHTML).toMatch(/<comp[^>]*>Some template<\/comp>/);
        });
      });

  onlyInIvy('patched ng defs should be removed after resetting TestingModule')
      .describe('resetting ng defs', () => {
        it('should restore ng defs to their initial states', () => {
          @Pipe({name: 'somePipe', pure: true})
          class SomePipe {
            transform(value: string): string { return `transformed ${value}`; }
          }

          @Directive({selector: 'someDirective'})
          class SomeDirective {
            someProp = 'hello';
          }

          @Component({selector: 'comp', template: 'someText'})
          class SomeComponent {
          }

          @NgModule({declarations: [SomeComponent]})
          class SomeModule {
          }

          TestBed.configureTestingModule({imports: [SomeModule]});

          // adding Pipe and Directive via metadata override
          TestBed.overrideModule(
              SomeModule, {set: {declarations: [SomeComponent, SomePipe, SomeDirective]}});
          TestBed.overrideComponent(
              SomeComponent,
              {set: {template: `<span someDirective>{{'hello' | somePipe}}</span>`}});
          TestBed.createComponent(SomeComponent);

          const cmpDefBeforeReset = (SomeComponent as any).ɵcmp;
          expect(cmpDefBeforeReset.pipeDefs().length).toEqual(1);
          expect(cmpDefBeforeReset.directiveDefs().length).toEqual(2);  // directive + component

          const modDefBeforeReset = (SomeModule as any).ɵmod;
          const transitiveScope = modDefBeforeReset.transitiveCompileScopes.compilation;
          expect(transitiveScope.pipes.size).toEqual(1);
          expect(transitiveScope.directives.size).toEqual(2);

          TestBed.resetTestingModule();

          const cmpDefAfterReset = (SomeComponent as any).ɵcmp;
          expect(cmpDefAfterReset.pipeDefs).toBe(null);
          expect(cmpDefAfterReset.directiveDefs).toBe(null);

          const modDefAfterReset = (SomeModule as any).ɵmod;
          expect(modDefAfterReset.transitiveCompileScopes).toBe(null);
        });

        it('should cleanup ng defs for classes with no ng annotations (in case of inheritance)',
           () => {
             @Component({selector: 'someDirective', template: '...'})
             class SomeComponent {
             }

             class ComponentWithNoAnnotations extends SomeComponent {}

             @Directive({selector: 'some-directive'})
             class SomeDirective {
             }

             class DirectiveWithNoAnnotations extends SomeDirective {}

             @Pipe({name: 'some-pipe'})
             class SomePipe {
             }

             class PipeWithNoAnnotations extends SomePipe {}

             TestBed.configureTestingModule({
               declarations: [
                 ComponentWithNoAnnotations, DirectiveWithNoAnnotations, PipeWithNoAnnotations
               ]
             });
             TestBed.createComponent(ComponentWithNoAnnotations);

             expect(ComponentWithNoAnnotations.hasOwnProperty('ɵcmp')).toBeTruthy();
             expect(SomeComponent.hasOwnProperty('ɵcmp')).toBeTruthy();

             expect(DirectiveWithNoAnnotations.hasOwnProperty('ɵdir')).toBeTruthy();
             expect(SomeDirective.hasOwnProperty('ɵdir')).toBeTruthy();

             expect(PipeWithNoAnnotations.hasOwnProperty('ɵpipe')).toBeTruthy();
             expect(SomePipe.hasOwnProperty('ɵpipe')).toBeTruthy();

             TestBed.resetTestingModule();

             // ng defs should be removed from classes with no annotations
             expect(ComponentWithNoAnnotations.hasOwnProperty('ɵcmp')).toBeFalsy();
             expect(DirectiveWithNoAnnotations.hasOwnProperty('ɵdir')).toBeFalsy();
             expect(PipeWithNoAnnotations.hasOwnProperty('ɵpipe')).toBeFalsy();

             // ng defs should be preserved on super types
             expect(SomeComponent.hasOwnProperty('ɵcmp')).toBeTruthy();
             expect(SomeDirective.hasOwnProperty('ɵdir')).toBeTruthy();
             expect(SomePipe.hasOwnProperty('ɵpipe')).toBeTruthy();
           });

        it('should clean up overridden providers for modules that are imported more than once',
           () => {

             @Injectable()
             class Token {
               name: string = 'real';
             }

             @NgModule({
               providers: [Token],
             })
             class Module {
             }

             TestBed.configureTestingModule({imports: [Module, Module]});
             TestBed.overrideProvider(Token, {useValue: {name: 'fake'}});

             expect(TestBed.inject(Token).name).toEqual('fake');

             TestBed.resetTestingModule();

             // The providers for the module should have been restored to the original array, with
             // no trace of the overridden providers.
             expect((Module as any).ɵinj.providers).toEqual([Token]);
           });

        it('should clean up overridden providers on components whose modules are compiled more than once',
           async() => {
             @Injectable()
             class SomeInjectable {
               id: string|undefined;
             }

             @Component({providers: [SomeInjectable]})
             class ComponentWithProvider {
               constructor(readonly injectable: SomeInjectable) {}
             }

             @NgModule({declarations: [ComponentWithProvider]})
             class MyModule {
             }

             TestBed.configureTestingModule({imports: [MyModule]});
             const originalResolver = (ComponentWithProvider as any).ɵcmp.providersResolver;
             TestBed.overrideProvider(SomeInjectable, {useValue: {id: 'fake'}});

             const compiler = TestBed.inject(Compiler);
             await compiler.compileModuleAsync(MyModule);
             compiler.compileModuleSync(MyModule);

             TestBed.resetTestingModule();
             expect((ComponentWithProvider as any).ɵcmp.providersResolver)
                 .toEqual(originalResolver);
           });
      });

  onlyInIvy('VE injects undefined when provider does not have useValue or useFactory')
      .describe('overrides provider', () => {
        it('with empty provider object', () => {
          @Injectable()
          class Service {
          }
          TestBed.overrideProvider(Service, {});
          // Should be able to get a Service instance because it has no dependencies that can't be
          // resolved
          expect(TestBed.inject(Service)).toBeDefined();
        });
      });

  onlyInIvy('uses Ivy-specific compiler output')
      .it('should handle provider overrides when module imports are provided as a function', () => {
        class InjectedString {
          value?: string;
        }

        @Component({template: '{{injectedString.value}}'})
        class AppComponent {
          constructor(public injectedString: InjectedString) {}
        }

        @NgModule({})
        class DependencyModule {
        }

        // We need to write the compiler output manually here,
        // because it depends on code generated by ngcc.
        class TestingModule {
          static ɵmod = defineNgModule({type: TestingModule});
          static ɵinj =
              defineInjector({factory: () => new TestingModule(), imports: [DependencyModule]});
        }
        setNgModuleScope(TestingModule, {imports: () => [DependencyModule]});

        TestBed
            .configureTestingModule({
              imports: [TestingModule],
              declarations: [AppComponent],
              providers: [{provide: InjectedString, useValue: {value: 'initial'}}],
            })
            .compileComponents();

        TestBed.overrideProvider(InjectedString, {useValue: {value: 'changed'}})
            .compileComponents();

        const fixture = TestBed.createComponent(AppComponent);
        fixture.detectChanges();
        expect(fixture !.nativeElement.textContent).toContain('changed');
      });
});